Prosecutors Allege Washington Businessman Spent More Than $600,000 on Help in Primaries

WASHINGTON—Federal prosecutors are questioning officials from Hillary Clinton's 2008 presidential campaign as part of an election-finance investigation involving a Washington, D.C., businessman and a mayoral election in the city.

Prosecutors allege in court documents that the businessman, Jeffrey Thompson, spent more than $600,000 on an undisclosed get-out-the-vote campaign to help Ms. Clinton in the 2008 Democratic primaries in Texas...